الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Infections of multidrug-resistant Gram-negative bacteria (MRGN) are a serious threat and a challenge to healthcare system. Carbapenems (imipenem, meropenem) have been used as “last-line agents” or “antibiotics of last resort” for treatment MDR bacteria such as Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae producing extended-spectrum β-lactamase (ESBL) in hospital settings due to their high potency, broad-spectrum activity and safety profile. Unfortunately, the emergence of Carbapenem-Resistant Gram-negative pathogens (CRGNB) has increased dramatically in the last decade threatening this class of lifesaving drugs.
World Health Organization developed a global priority pathogens list (global PPL) of antibiotic-resistant bacteria to help in prioritizing the research and development of new and effective antibiotic treatments. The pathogens were grouped according to the species and the type of resistance into three priority categories: critical, high and medium. The critical priority category included carbapenem-resistant Acinetobacter baumannii, ranked as number one. The objective of the study is to evaluate the prevalence of carbapenem resistant among Gram negtive pathogens and study the genotypic variation of carbapenem resistant genes belonging to carbapenem hydrolysing class D β-
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lactamases (CHDL) -“OXA-type β-lactamases” in A.baumannii isolates from three Egyptian hospitals.
Gram negative isolates were collected from different hospitals in Egypt, and identified to the species level by Vitek 2 automated system. Antibiotic susceptibility test was carried out by Vitek 2. Acinetobacter baumannii was reported the highest MDR and carbapenem resistant bacteria. MICs for carbapenems (IPM and MEM) were carried out by agar well diffusion method for forty carbapenem resistant A.baumannii isolates (CRAB). Plasmid curing with acridine orange along with antibiotic susceptibility by disc diffusion for IPM and MEM were carried out before & after treatment to determine the origin of carbapenem resistance. CRAB isolates were screened for the main four OXA- type groups by PCR: OXA-23-Like, OXA-24-Like, OXA-51-like and OXA-58-like. Results showed that almost all of the CRAB isolates were extensive drug resistant (XDR) and pan drug resistant (PDR). OXA-51- like genes were the most prevalent carried by 95% of isolates followed by OXA-23-like genes and OXA-24-like genes, 90% each .while OXA-58-like genes were not detected. OXA-51 gene was not detected in 5% of chromosomally mediated carbapenem resistance isolates, proving the inconvenience of using OXA-51 gene as a species specific region for identification of CRAB. OXA-24 gene was rarely identified in Egypt and its prevalence in this study is the first to
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be reported in Egypt. The co-existence of multiple OXA genes were reported in all of the tested CRAB isolates, 75% were OXA-23/OXA-24/OXA-51 carriers, 10% were OXA-23/OXA-51 carriers, 10% were OXA-24/OXA-51 carriers and 5% were OXA-23/OXA-24 carriers. This study provides an epidemiological snapshot on CRAB population and OXA-type carbapenemase in Egypt